I installed a stereo in my car a while ago and the ground to the head unit was bad. I ran a new wire from the head unit and connected it to where the stereo frame and the floor pan meet (the bolt that holds the dash to the floor). Now I get hum in the speakers occasionally. Is it just that where it is ground is not a good spot or could it be something else? Where is a good ground spot? Would finding a better spot fix the problem.